titles in create study wizard (subjects and events) are not shown in IE7

Description

When I go to the study create wizard, to the step 'subjects' or 'events', the table containing the objects is not correctly shown. The titles above the columns are invisible (see screenshot). Maybe the contents of the header line is moved down a bit, since the first line has contains a mess of inputs and images.

I think this has to do with IE7, since I didn't see it on my home computer.